Method Of Manufacturing Three-Dimensional Shaped Object And Three-Dimensional Shaped Object

ABSTRACT

A method of manufacturing a three-dimensional shaped object includes: a powder layer forming step of leveling a Fe-based metal powder to form a powder layer; a binder applying step of applying a binder solution to a formation region of the powder layer corresponding to a laminate-shaped body to be formed; an ink applying step of applying an ink containing carbon particles to the formation region such that an amount of the carbon particles supplied to the formation region is partially varied; a repeating step of, when the formation region to which the binder solution and the ink are applied is set as a unit layer, obtaining the laminate-shaped body in which a plurality of the unit layers are laminated; a sintering step of performing a sintering treatment on the laminate-shaped body to obtain a metal sintered body; and a quenching step of performing a quenching treatment to obtain a three-dimensional shaped object.

The present application is based on, and claims priority from JPApplication Serial Number 2022-006171, filed Jan. 19, 2022, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a method of manufacturing athree-dimensional shaped object and a three-dimensional shaped object.

2. Related Art

In recent years, as a technique for shaping a three-dimensional object,a lamination shaping method using a metal powder has been widely used.This technique includes a step of calculating a cross-sectional shape ofa three-dimensional object obtained by thinly slicing thethree-dimensional object on a plane orthogonal to a laminatingdirection, a step of forming a powder layer by layering a metal powder,and a step of solidifying a part of the powder layer based on the shapeobtained by the calculation. In this technique, the three-dimensionalobject is shaped by repeating the step of forming a powder layer and thestep of solidifying a part of the powder layer.

For example, JP-A-2020-066139 discloses a method of manufacturing athree-dimensional shaped object in which a green body is obtained byrepeating a layer forming step of forming a layer of a granulated powderand a binder applying step of applying a binder to the layer to form ashape, and then the obtained green body is sintered to obtain a sinteredbody.

The method described in JP-A-2020-066139 has the following problems. Forexample, when the metal powder having a high carbon content is used,toughness of the three-dimensional shaped object decreases. Therefore,durability of the three-dimensional shaped object is likely to decrease.

In addition, a method is known in which a three-dimensional shapedobject is obtained using a metal powder having a low carbon content, andthen a carburizing treatment is performed on a surface of thethree-dimensional shaped object. In this method, the surface can behardened in a state in which the carbon content in the three-dimensionalshaped object is kept low. However, in this method, since it isnecessary to add the carburizing treatment after manufacturing thethree-dimensional shaped object, advantages of the lamination shapingmethod, such as simplicity and low cost, are impaired.

SUMMARY

Therefore, an object of the present disclosure is to provide a method ofmanufacturing a three-dimensional shaped object having both hightoughness and high surface hardness without impairing advantages of alamination shaping method.

A method of manufacturing a three-dimensional shaped object according toan application example of the present disclosure includes: a powderlayer forming step of leveling a Fe-based metal powder on a table toform a powder layer;

a binder applying step of applying a binder solution containing a binderto a formation region of the powder layer corresponding to alaminate-shaped body to be formed;

an ink applying step of applying an ink containing carbon particles tothe formation region such that an amount of the carbon particlessupplied to the formation region is partially varied;

a repeating step of repeating the powder layer forming step, the binderapplying step, and the ink applying step one or more times, when theformation region to which the binder solution and the ink are applied isset as a unit layer, to obtain the laminate-shaped body in which aplurality of the unit layers are laminated;

a sintering step of performing a sintering treatment on thelaminate-shaped body to obtain a metal sintered body; and

a quenching step of performing a quenching treatment on the metalsintered body to obtain a three-dimensional shaped object.

A method of manufacturing a three-dimensional shaped object according toan application example of the present disclosure includes:

a powder layer forming step of leveling a Fe-based metal powder on atable to form a powder layer;

an ink impregnating step of impregnating a formation region of thepowder layer corresponding to a metal sintered body to be formed with anink containing carbon particles such that an amount of the carbonparticles to be supplied is partially varied, so as to obtain an inkimpregnated layer;

an energy ray irradiating step of irradiating the formation regionincluding at least the ink impregnated layer with an energy ray toobtain a sintered layer;

a repeating step of repeating the powder layer forming step, the inkimpregnating step, and the energy ray irradiating step one or more timesto obtain the metal sintered body in which a plurality of the sinteredlayers are laminated; and

a quenching step of performing a quenching treatment on the metalsintered body to obtain a three-dimensional shaped object.

A three-dimensional shaped object according to an application example ofthe present disclosure is made of a sintered material of a Fe-basedmetal powder and has a portion in which a carbon concentration decreasesfrom an outer surface toward an inner portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a process diagram showing a method of manufacturing athree-dimensional shaped object according to a first embodiment.

FIG. 2 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 3 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 4 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 5 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 6 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 7 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 8 is a cross-sectional view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 9 is a plan view showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 .

FIG. 10 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 11 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 12 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 13 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 14 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 15 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 16 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 1 .

FIG. 17 is a process diagram showing a method of manufacturing athree-dimensional shaped object according to a second embodiment.

FIG. 18 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 17 .

FIG. 19 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 17 .

FIG. 20 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 17 .

FIG. 21 is a cross-sectional view showing the method of manufacturingthe three-dimensional shaped object shown in FIG. 17 .

FIG. 22 is a cross-sectional view schematically showing a distributionof a carbon concentration in a three-dimensional shaped object accordingto a third embodiment.

FIG. 23 is a top view schematically showing a distribution of a carbonconcentration in a three-dimensional shaped object according to amodification.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of a method of manufacturing athree-dimensional shaped object and a three-dimensional shaped objectaccording to the present disclosure will be described in detail withreference to the accompanying drawings.

1. First Embodiment

First, a method of manufacturing a three-dimensional shaped objectaccording to a first embodiment will be described.

FIG. 1 is a process diagram showing the method of manufacturing thethree-dimensional shaped object according to the first embodiment. FIGS.2 to 8 are cross-sectional views showing the method of manufacturing thethree-dimensional shaped object shown in FIG. 1 . FIG. 9 is a plan viewshowing the method of manufacturing the three-dimensional shaped objectshown in FIG. 1 . FIGS. 10 to 16 are cross-sectional views showing themethod of manufacturing the three-dimensional shaped object shown inFIG. 1 . In the drawings of the present application, an X axis, a Yaxis, and a Z axis are set as three axes orthogonal to each other. Eachaxis is represented by an arrow, and a tip end side is referred to as a“plus side” and a base end side is referred to as a “minus side”. In thefollowing description, in particular, the plus side of the Z axis isreferred to as “upper”, and the minus side of the Z axis is referred toas “lower”. In addition, both directions parallel to the X axis arereferred to as an X axis direction, both directions parallel to the Yaxis are referred to as a Y axis direction, and both directions parallelto the Z axis are referred to as a Z axis direction.

The method of manufacturing the three-dimensional shaped objectaccording to the first embodiment is a method called a binder jetmethod, and includes a powder layer forming step S102, a binder applyingstep S104, an ink applying step S106, a repeating step S108, a sinteringstep S110, and a quenching step S112 as shown in FIG. 1 .

In the powder layer forming step S102, a Fe-based metal powder 1 isleveled on a shaping stage 23 (on a table) to form a powder layer 31. Inthe binder applying step S104, a binder solution 4 is applied to aformation region 60 of the powder layer 31 corresponding to alaminate-shaped body 6 to be shaped. In the ink applying step S106, anink 5 containing carbon particles is applied to the formation region 60of the powder layer 31. In the repeating step S108, the powder layerforming step S102, the binder applying step S104, and the ink applyingstep S106 are repeated one or more times. Accordingly, when theformation region 60 to which the binder solution 4 and the ink 5 areapplied is set as an ink applying layer 51 (unit layer), a plurality ofthe ink applying layers 51 are laminated to obtain the laminate-shapedbody 6. In the sintering step S110, a sintering treatment is performedon the laminate-shaped body 6 to obtain a metal sintered body. In thequenching step S112, a quenching treatment is performed on the metalsintered body to obtain a three-dimensional shaped object 10.Hereinafter, each step will be sequentially described.

1.1. Lamination Shaping Device

First, a lamination shaping device 2 will be described as an example ofa device used in the method of manufacturing the three-dimensionalshaped object according to the first embodiment.

The lamination shaping device 2 includes a device main body 21 includinga powder storage unit 211 and a shaping unit 212, a powder supplyelevator 22 provided in the powder storage unit 211, a shaping stage 23provided in the shaping unit 212, and a coater 24, a roller 25, and aliquid supply unit 26 provided movably on the device main body 21.

The powder storage unit 211 is a recessed portion provided in the devicemain body 21 and having an open upper portion. The Fe-based metal powder1 is stored in the powder storage unit 211. An appropriate amount of theFe-based metal powder 1 stored in the powder storage unit 211 issupplied to the shaping unit 212 by the coater 24.

The powder supply elevator 22 is disposed at a bottom portion of thepowder storage unit 211. The powder supply elevator 22 is movable in theZ axis direction in a state where the Fe-based metal powder 1 is placedon the powder supply elevator 22. By moving the powder supply elevator22 upward, the Fe-based metal powder 1 placed on the powder supplyelevator 22 is pushed up and protrudes from the powder storage unit 211.Accordingly, the protruded Fe-based metal powder 1 can be moved to theshaping unit 212 side by the coater 24.

The shaping unit 212 is a recessed portion provided in the device mainbody 21 and having an open upper portion. The shaping stage 23 isdisposed inside the shaping unit 212. On the shaping stage 23, theFe-based metal powder 1 is leveled by the coater 24 and laid in layers.In addition, the shaping stage 23 is movable in the Z axis direction ina state where the Fe-based metal powder 1 is laid on the shaping stage23. By appropriately setting a height of the shaping stage 23, an amountof the Fe-based metal powder 1 laid on the shaping stage 23 can beadjusted.

The coater 24 and the roller 25 are movable in the X axis direction fromthe powder storage unit 211 to the shaping unit 212. The coater 24 canlevel and lay the Fe-based metal powder 1 in layers by pulling theFe-based metal powder 1. The roller 25 compresses the leveled Fe-basedmetal powder 1 from above.

The liquid supply unit 26 is implemented by, for example, an inkjet heador a dispenser, and is movable in the X axis direction and the Y axisdirection in the shaping unit 212. The liquid supply unit 26 can supplya target amount of the binder solution 4 or the ink 5 to a targetposition. The liquid supply unit 26 may include a plurality of dispensenozzles in one head. The binder solution 4 may be dispensed from onedispense nozzle, and the ink 5 may be dispensed from another dispensenozzle. In addition, a head for supplying the binder solution 4 and ahead for supplying the ink 5 may be separate members.

1.2. Powder Layer Forming Step

In the powder layer forming step S102, the Fe-based metal powder 1 islaid on the shaping stage 23 to form the powder layer 31. Specifically,as shown in FIGS. 2 and 3 , the Fe-based metal powder 1 stored in thepowder storage unit 211 is pulled onto the shaping stage 23 by using thecoater 24, and the Fe-based metal powder 1 is leveled to a uniformthickness. Accordingly, the powder layer 31 shown in FIG. 4 is obtained.At this time, a thickness of the powder layer 31 can be adjusted bylowering an upper surface of the shaping stage 23 below an upper end ofthe shaping unit 212 and adjusting an amount by which the upper surfaceof the shaping stage 23 is lowered.

Next, the roller 25 is moved in the X axis direction while the powderlayer 31 is compressed in a thickness direction by the roller 25.Accordingly, a filling rate of the Fe-based metal powder 1 in the powderlayer 31 can be increased. The compression by the roller 25 may beperformed as necessary, and may be omitted. In addition, the powderlayer 31 may be compressed by a unit different from the roller 25, forexample, a pressing plate.

A constituent material of the Fe-based metal powder 1 is notparticularly limited as long as the constituent material is a metalmaterial containing Fe as a main component. An example of theconstituent material is a Fe-based metal material in which improvementin hardness is expected by adding carbon particles and performing aquenching treatment. The Fe-based metal material is not particularlylimited, and examples thereof include stainless steel, steel formechanical structure, tool steel, high-speed steel, die steel, bearingsteel, and alloy steel.

In addition, if necessary, the surface of the Fe-based metal powder 1may be subjected to any surface treatment such as a silane couplingagent treatment.

In addition, a method of manufacturing the Fe-based metal powder 1 isnot particularly limited, and examples thereof include variousatomization methods such as a water atomization method and a gasatomization method, and a pulverization method. Among these, a powdermanufactured by the water atomization method often has an oxide film onparticle surfaces. The oxide film reacts with the carbon particles andis reduced in a sintering treatment or the like to be described later.Therefore, when the Fe-based metal powder 1 having an oxide film isused, an amount of the carbon particles contained in the ink 5 describedlater or an amount of the ink 5 supplied to the formation region 60 maybe adjusted in consideration of the consumption of the carbon particlesdue to the reduction.

1.3. Binder Applying Step

In the binder applying step S104, as shown in FIG. 5 , the liquid supplyunit 26 supplies the binder solution 4 to the formation region 60 of thepowder layer 31 corresponding to the laminate-shaped body 6 to beshaped. The binder solution 4 is a liquid containing a binder and asolvent or a dispersion medium. In the formation region 60 to which thebinder solution 4 is supplied, the particles of the Fe-based metalpowder 1 are bound to each other, and a binding layer 41 shown in FIG. 6is obtained. In the binding layer 41, the particles of the Fe-basedmetal powder 1 are bound to each other by the binder, and the Fe-basedmetal powder 1 has a shape retention property that is not broken due toits own weight.

The binding layer 41 may be heated simultaneously with or after thesupply of the binder solution 4. Accordingly, volatilization of thesolvent or the dispersion medium contained in the binder solution 4 ispromoted, and binding of the particles due to solidification or curingof the binder is promoted. When the binder contains a photocurable resinor an ultraviolet curable resin, light irradiation or ultravioletirradiation may be performed instead of or in combination with heating.

A heating temperature during heating is not particularly limited, and ispreferably 50° C. or higher and 250° C. or lower, and more preferably70° C. or higher and 200° C. or lower. Accordingly, when the Fe-basedmetal powder 1 not bound by the binder solution 4 is reused, it ispossible to prevent the Fe-based metal powder 1 from being denatured dueto heating.

The binder solution 4 is not particularly limited as long as the bindersolution 4 is a liquid having a component capable of binding theparticles of the Fe-based metal powder 1 to each other. Examples of thesolvent or dispersion medium contained in the binder solution 4 includewater, alcohols, ketones, and carboxylic acid esters, and the solvent ordispersion medium may be a mixed liquid containing at least one of theabove. In addition, examples of the binder contained in the bindersolution 4 include fatty acids, paraffin wax, microwax, polyethylene,polypropylene, polystyrene, acrylic resins, polyamide resins,polyesters, stearic acid, polyvinylpyrrolidone (PVP), polyvinyl alcohol(PVA), and polyethylene glycol (PEG).

1.4. Ink Applying Step

In the ink applying step S106, the ink 5 is supplied to the formationregion 60 of the powder layer 31. The ink 5 is a liquid containingcarbon particles and a dispersion medium. In the present embodiment, theink 5 is supplied to the binding layer 41 shown in FIG. 7 correspondingto the formation region 60. Accordingly, the binding layer 41 can beimpregnated with the ink 5. As a result, carbon particles are applied tothe binding layer 41, and the ink applying layer 51 (unit layer) shownin FIG. 8 is obtained. At this time, an amount of carbon particlessupplied to the binding layer 41 is partially varied. The amount of thecarbon particles depends on hardness of a quenched structure in thequenching treatment described later. The quenched structure due tomartensitic transformation exhibits high hardness and properties such aswear resistance. On the other hand, the quenched structure may cause adecrease in toughness. Therefore, by forming a quenched structure inwhich hardness is partially adjusted only in a necessary portion, it ispossible to finally obtain the three-dimensional shaped object 10 havingboth high toughness and high hardness.

In the present embodiment, as shown in FIG. 8 , a gradient is formed inwhich the amount of the carbon particles decreases from an outer edgeportion of the ink applying layer 51 toward an inner portion (a portionother than the outer edge portion). FIG. 8 is a partially enlarged viewof the ink applying layer 51 shown in FIG. 7 . In FIG. 8 , the gradientof the amount of the carbon particles, in other words, a gradient of aconcentration of the carbon particles is represented by an inclinationof an arrow C1. In the example of FIG. 8 , the arrow C1 is inclined suchthat the inner portion of the ink applying layer 51 is lower than theouter edge portion of the ink applying layer 51. By providing such agradient of the concentration, finally, the three-dimensional shapedobject 10 having high surface hardness and high internal toughness isobtained. The gradient of the concentration may be a smooth gradient (agradient in which the inclination continuously changes) or a stepwisegradient (a gradient in which the inclination discontinuously changes).It is sufficient that the gradient is macroscopically provided as awhole, and in consideration of decarburization during sintering, aportion having a high concentration may be present in the vicinity ofthe surface. In addition, in this step, the amount of carbon particlesto be supplied may be partially varied, and thus a pattern of thegradient is not particularly limited. For example, a part of theformation region 60 may include a region to which the ink 5 is notsupplied at all (a region in which the amount of carbon particles to besupplied is zero).

FIG. 9 is a plan view of the ink applying layer 51 shown in FIG. 8 . InFIG. 9 , the gradient of the concentration of the carbon particles isrepresented by a density of dots. In the example of FIG. 9 , an outeredge of the ink applying layer 51 has a circular shape, and theconcentration of the carbon particles increases radially from the centertoward the outer edge. A pattern of the gradient of the concentration isnot limited to the shown pattern. For example, in a part of the outeredge, the gradient of the concentration may be partially steeper orgentler than in the other parts. In addition, the binder applying stepS104 and the ink applying step S106 may be performed in a reverse order.That is, after the ink 5 is applied to the formation region 60, thebinder solution 4 may be applied, and the obtained layer may be used asthe ink applying layer 5 (unit layer).

The carbon particles are particles composed of a material containing asimple substance carbon as a main component, and examples of the carbonparticles include graphite particles, carbon black, carbon fibers, andcarbon nanotubes. The term “main component” refers to a component thataccounts for 50.0% by mass or more. The carbon particles are preferablyparticles in which 90.0% by mass or more of the component is the simplesubstance carbon.

The carbon particles are particularly preferably carbon black. Thecarbon black is an industrially manufactured carbon powder, and hasuniform surface properties such as the presence of various functionalgroups on the particle surfaces. Therefore, the ink 5 containing thecarbon black as the carbon powder is excellent in stability, and can besupplied such that the carbon particles are uniformly distributed.

An average particle diameter of the carbon particles is preferably1/100000 or more and 1/100 or less, more preferably 1/50000 or more and1/500 or less, and still more preferably 1/10000 or more and 1/1000 orless of an average particle diameter of the Fe-based metal powder 1.Accordingly, it is easier for the carbon particles to penetrate gapsbetween the particles of the Fe-based metal powder 1. Therefore, whenthe ink 5 is supplied to the formation region 60, the carbon particlesare easily distributed along the surfaces of the particles of theFe-based metal powder 1. As a result, the quenching treatment to bedescribed later can be performed more uniformly.

The average particle diameter of the carbon particles is preferably 10nm or more and 10 μm or less, and more preferably 10 nm or more and 5 μmor less. The average particle diameter of the carbon particles refers toa particle diameter when a cumulative mass based on volume is 50% usinga laser diffraction particle size distribution analyzer. In addition, inthe ink 5, the carbon particles may be aggregated to form secondaryparticles. In this case, a particle diameter of the secondary particlesis set as the particle diameter of the carbon particles.

Examples of the dispersion medium include water, an organic solvent, anda mixture of water and an organic solvent. Among these, examples ofwater include ion exchange water, ultrafiltrated water, reverse osmosiswater, distilled water, pure water, and ultrapure water. Examples of theorganic solvent include a water-soluble solvent and a water-insolublesolvent.

A content of the carbon particles in the ink 5 is appropriately setdepending on a supply method of the ink 5, and is preferably 0.1% bymass or more and 50.0% by mass or less, more preferably 1.0% by mass ormore and 30.0% by mass or less, still more preferably 2.0% by mass ormore and 20.0% by mass or less, and particularly preferably 5.0% by massor more and 20.0% by mass or less. By setting the content of the carbonparticles in the ink 5 within the above range, both the ease of handlingof the ink 5 and a supply efficiency of the carbon particles can beachieved. When the content of the carbon particles in the ink 5 is lessthan the lower limit value, the supply efficiency decreases, and a largeamount of the ink 5 needs to be supplied to the formation region 60, andthus a mechanical strength of the ink applying layer 51 may decrease.When the content of the carbon particles in the ink 5 exceeds the upperlimit value, a viscosity of the ink 5 is too high, and thus, dependingon the supply method, handleability of the ink 5 may decrease.

Additives other than the above components may be added to the ink 5.Examples of the additive include a dispersant, a surfactant, a wettingagent (anti-drying agent), an antioxidant, an ultraviolet absorber, apenetration accelerator, a preservative, an antifungal agent, a pHadjuster, a viscosity adjuster, and a chelating agent.

1.5. Repeating Step

In the repeating step S108, when the formation region 60 to which thebinder solution 4 and the ink 5 are applied is set as the ink applyinglayer 51 (unit layer), the powder layer forming step S102, the binderapplying step S104, and the ink applying step S106 are repeated one ormore times until a laminated body formed by laminating the plurality ofink applying layers 51 has a predetermined shape. That is, these stepsare performed twice or more in total. Accordingly, the three-dimensionallaminate-shaped body 6 shown in FIG. 15 is obtained.

Specifically, first, as shown in FIG. 10 , a new powder layer 31 isformed at the ink applying layer 51 shown in FIG. 8 . Next, as shown inFIG. 11 , the binder solution 4 is supplied to the formation region 60of the powder layer 31. Accordingly, the binding layer 41 shown in FIG.12 is obtained.

Next, the ink 5 is supplied to the formation region 60 of the powderlayer 31. In the present embodiment, the ink 5 is supplied to thebinding layer 41 shown in FIG. 12 . Accordingly, the ink applying layer51 shown in FIG. 13 is obtained. FIG. 14 is a partially enlarged view ofthe ink applying layer 51 shown in FIG. 13 . In FIG. 14 , the gradientof the concentration of the carbon particles is represented by aninclination of an arrow C2. In the example of FIG. 14 , the arrow C2 isalso inclined such that the inner portion of the ink applying layer 51is lower than the outer edge portion of the ink applying layer 51.

The inclination of the arrow C2 shown in FIG. 14 may be the same as theinclination of the arrow C1 shown in FIG. 8 , and is preferablydifferent from the inclination of the arrow C1. Accordingly, thegradient of the concentration of the carbon particles can be optimizedaccording to a shape of the three-dimensional shaped object 10.

As described above, the laminate-shaped body 6 shown in FIG. 15 is alaminated body of the plurality of ink applying layers 51 (unit layers).In the powder layer 31, the Fe-based metal powder 1 that does notconstitute the ink applying layer 51 is recovered and reused asnecessary. In addition, when the repeating step S108 is repeated twiceor more, the application of the ink 5 may be omitted in some of therepeating steps S108. Further, when the repeating step S108 is repeatedtwice or more, in some of the repeating steps S108, the amount of thecarbon particles supplied to the formation region 60 may not bepartially varied.

1.6. Sintering Step

In the sintering step S110, the sintering treatment is performed on thelaminate-shaped body 6. In the sintering treatment, the laminate-shapedbody 6 is heated to cause a sintering reaction. Accordingly, the metalsintered body is obtained.

A sintering temperature varies depending on a type, a particle diameter,or the like of the Fe-based metal powder 1. As an example, the sinteringtemperature is preferably 980° C. or higher and 1330° C. or lower, andmore preferably 1050° C. or higher and 1260° C. or lower. In addition, asintering time is preferably 0.2 hours or longer and 7 hours or shorter,and more preferably 1 hour or longer and 6 hours or shorter.

Examples of an atmosphere in the sintering treatment include a reducingatmosphere such as hydrogen, an inert atmosphere such as nitrogen andargon, and a reduced-pressure atmosphere obtained by reducing theseatmospheres. A pressure in the reduced-pressure atmosphere is notparticularly limited as long as the pressure is less than normalpressure (100 kPa). The pressure is preferably 10 kPa or less, and morepreferably 1 kPa or less.

1.7. Quenching Step

In the quenching step S112, the quenching treatment is performed on themetal sintered body. The quenching treatment is a treatment of heatingthe metal sintered body and then rapidly cooling the metal sinteredbody. Accordingly, in a region where the carbon concentration isincreased to a predetermined concentration, a metal structure istransformed from austenite to martensite, and accordingly becomes aquenched structure derived from martensite, and has high hardness.Changing into such a quenched structure is referred to as “quenching”.On the other hand, in a region where the carbon concentration is notincreased, since the quenched structure is not formed, the hardness isnot increased. By such a quenching treatment, the three-dimensionalshaped object 10 shown in FIG. 16 is obtained.

A quenching temperature is, for example, 950° C. or higher and 1200° C.or lower. In addition, a quenching time is, for example, 0.2 hours orlonger and 3 hours or shorter. For the rapid cooling, water cooling, oilcooling, or the like is used.

After the quenching treatment, a tempering treatment may be performed asnecessary. The tempering treatment is a treatment in which the metalsintered body after the quenching treatment is heated again at atemperature lower than that of the quenching treatment. Accordingly, thetoughness can be applied to the metal sintered body while the hardnessof the metal sintered body is slightly reduced.

A tempering temperature is, for example, 100° C. or higher and 250° C.or lower. In addition, a tempering time is, for example, 0.3 hours orlonger and 5 hours or shorter.

1.8. Effects of First Embodiment

As described above, the method of manufacturing the three-dimensionalshaped object according to the first embodiment includes the powderlayer forming step S102, the binder applying step S104, the ink applyingstep S106, the repeating step S108, the sintering step S110, and thequenching step S112. In the powder layer forming step S102, the Fe-basedmetal powder 1 is leveled on the shaping stage 23 (on the table) to formthe powder layer 31. In the binder applying step S104, the bindersolution 4 containing the binder is applied to the formation region 60of the powder layer 31 corresponding to the laminate-shaped body 6 to beformed. In the ink applying step S106, the ink 5 containing the carbonparticles is applied to the formation region 60 such that the amount ofthe carbon particles supplied to the formation region 60 is partiallyvaried. In the repeating step S108, when the formation region 60 towhich the binder solution 4 and the ink 5 are applied is set as the inkapplying layer 51 (unit layer) , the powder layer forming step S102, thebinder applying step S104, and the ink applying step S106 are repeatedone or more times to obtain the laminate-shaped body 6 in which theplurality of ink applying layers 51 are laminated. In the sintering stepS110, the sintering treatment is performed on the laminate-shaped body 6to obtain the metal sintered body. In the quenching step S112, thequenching treatment is performed on the metal sintered body to obtainthe three-dimensional shaped object 10.

According to such a configuration, by partially varying the amount ofthe carbon particles supplied to the formation region 60, it is possibleto partially vary the degree of quenching in the finally obtainedthree-dimensional shaped object 10, that is, the hardness of thequenched structure. Accordingly, for example, in the vicinity of thesurface of the three-dimensional shaped object 10, the degree ofquenching can be increased to increase the hardness. On the other hand,inside the three-dimensional shaped object 10, the degree of quenchingcan be decreased to prevent an increase in the hardness. As a result, itis possible to implement the three-dimensional shaped object 10 havinghigh surface hardness and high internal toughness. In such athree-dimensional shaped object 10, both the high toughness and the highhardness are achieved, and thus, for example, both wear resistance anddurability are achieved.

In addition, according to the above-described method, it is possible toenjoy advantages of the binder jet method, which is a lamination shapingmethod, without impairing the advantages of the binder jet method.Therefore, for example, a region having a cavity therein can be set asthe formation region 60. Accordingly, a hollow structure can be easilyformed, a weight of the formation region 60 can be reduced, and finally,the three-dimensional shaped object 10 having high surface hardness anda light weight can be obtained.

In addition, in the method of manufacturing the three-dimensional shapedobject according to the first embodiment, the ink 5 is applied such thatthe amount of the carbon particles supplied to the outer edge portion ofthe formation region 60 is larger than the amount of the carbonparticles supplied to a portion other than the outer edge portion of theformation region 60.

By shaping the laminate-shaped body 6 using the formation region 60obtained in this manner and finally obtaining the three-dimensionalshaped object 10, it is possible to efficiently manufacture thethree-dimensional shaped object 10 having high surface hardness and highinternal toughness.

In addition, by providing a gradient in which the concentration of thecarbon particles continuously changes, it is possible to preventoccurrence of cracking or the like due to a difference in thermalexpansion between a quenched structure layer in the vicinity of thesurface and the internal metal structure in the three-dimensional shapedobject 10. Accordingly, reliability of the three-dimensional shapedobject 10 can be improved.

In addition, in the repeating step S108, when the ink applying layers 51(unit layers) are laminated, the amount of the carbon particles may bevaried between the ink applying layers 51. For example, in FIG. 14 , theinclination of the arrow C1 representing the gradient of theconcentration of the carbon particles in the first ink applying layer 51is different from the inclination of the arrow C2 representing thegradient of the concentration of the carbon particles in the second inkapplying layer 51. This variation corresponds to a variation of theamount of the carbon particles between the ink applying layers 51.

According to such a configuration, the amount of the carbon particles tobe supplied can be optimized according to the shape of thethree-dimensional shaped object 10. Accordingly, a thickness of a layerhaving high hardness can be optimized according to the shape of thethree-dimensional shaped object 10, and a balance between the highhardness and the high toughness of the three-dimensional shaped object10 can be optimized.

When the ink 5 is applied, the amount of the carbon particles to besupplied is adjusted such that the carbon concentration in thethree-dimensional shaped object 10 is preferably 0.2% by mass or more,and more preferably 0.3% by mass or more and 2.2% by mass or less.

According to such a configuration, it is possible to more reliably causequenching by the quenching treatment. The carbon concentrationimmediately after being supplied by the ink 5 may decrease due to thesubsequent steps. Therefore, the amount of the carbon particles to besupplied by the ink 5 is preferably set in consideration of the decreasein the concentration.

In addition, as shown in FIGS. 7 and 12 , it is preferable that the inkapplying step S106 includes, when the ink 5 is dispensed as liquiddroplets from a plurality of aligned nozzles, an operation of partiallyvarying the amount of the carbon particles by changing a density of theliquid droplets dispensed in a unit area.

When the ink 5 is dispensed from the plurality of nozzles included inthe liquid supply unit 26, control of selecting a nozzle from which theink 5 is to be dispensed is easy and accurate, and therefore, accordingto the above operation, the amount of the carbon particles to besupplied to the unit area can be easily and accurately controlled.Accordingly, finally, it is possible to easily manufacture thethree-dimensional shaped object 10 having a target carbon concentrationat a target position.

In the binder applying step S104 and the ink applying step S106, theapplication of the binder solution 4 and the application of the ink 5may be performed substantially simultaneously. That is, the bindersolution 4 and the ink 5 may be dispensed substantially simultaneouslyfrom the same head or different heads. Accordingly, throughput of thebinder applying step S104 and the ink applying step S106 can beincreased. The term “substantially simultaneously” means that a timedifference is 1 second or shorter.

On the other hand, in consideration of mixing of the dispensed bindersolution 4 and ink 5, it is preferable to provide a time differencebetween the application of the binder solution 4 and the application ofthe ink 5.

Alternatively, the binder solution 4 and the ink 5 may be mixed to forma mixed liquid, and the mixed liquid may be dispensed. That is, thebinder applying step S104 and the ink applying step S106 may besimultaneously performed by applying a liquid containing both the binderand the carbon particles to the formation region 60. Accordingly, thethroughput of the binder applying step S104 and the ink applying stepS106 can be increased.

In addition, the sintering treatment and the quenching treatment may beperformed by different processing devices, or may be performed by oneprocessing device. That is, after the completion of the sinteringtreatment, by keeping the laminate-shaped body 6 in the processingdevice, the sintering treatment and the quenching treatment may becontinuously performed without lowering a temperature of thelaminate-shaped body 6 to room temperature (25° C.)

According to such a configuration, since the sintering step S110 and thequenching step S112 can be continuously performed, the throughput ofthese steps can be increased.

In addition, the powder layer forming step S102 may include an operationof compressing the powder layer 31 in the thickness direction. By thisoperation, the filling rate of the Fe-based metal powder 1 in the powderlayer 31 can be increased. Accordingly, when the Fe-based metal powder 1having a high bulk density is used, the density of the three-dimensionalshaped object 10 can be finally increased.

2. Second Embodiment

Next, a method of manufacturing a three-dimensional shaped objectaccording to a second embodiment will be described.

FIG. 17 is a process diagram showing the method of manufacturing thethree-dimensional shaped object according to the second embodiment.FIGS. 18 to 21 are cross-sectional views showing the method ofmanufacturing the three-dimensional shaped object shown in FIG. 17 .

Hereinafter, the second embodiment will be described, and in thefollowing description, differences from the first embodiment will bemainly described, and description of similar matters will be omitted. Inthe drawings, the same components as those of the first embodiment aredenoted by the same reference numerals.

The method of manufacturing the three-dimensional shaped objectaccording to the second embodiment is a method called a selective lasersintering (SLS) method, and includes a powder layer forming step S202,an ink impregnating step S204, an energy ray irradiating step S206, arepeating step S208, and a quenching step S210 as shown in FIG. 17 .

2.1. Lamination Shaping Device

First, a lamination shaping device 2A will be described as an example ofa device used in the method of manufacturing the three-dimensionalshaped object according to the second embodiment.

The lamination shaping device 2A is the same as the lamination shapingdevice 2 described above except that an energy ray irradiating unit 27is added.

As shown in FIG. 19 , the energy ray irradiating unit 27 can irradiateany position on the shaping stage 23 with an energy ray E. Examples ofthe energy ray E include a laser beam and an electron beam. By theirradiation with the energy ray E, it is possible to cause a sinteringreaction between the particles of the Fe-based metal powder 1.

2.2. Powder Layer Forming Step

In the powder layer forming step S202, similar to the powder layerforming step S102 of the first embodiment, the Fe-based metal powder 1is leveled on the shaping stage 23 (on the table) to form the powderlayer 31.

2.3. Ink Impregnating Step

In the ink impregnating step S204, the ink 5 is supplied to theformation region 60 of the powder layer 31 corresponding to a metalsintered body 7 to be formed. Accordingly, the formation region 60 canbe impregnated with the ink 5. As a result, an ink impregnated layer 52shown in FIG. 19 is obtained. At this time, the amount of the carbonparticles supplied to the formation region 60 is partially varied.Specifically, similar to the gradient of the concentration indicated bythe arrow C1 in FIG. 8 , a gradient of a concentration of the carbonparticles is provided such that a concentration in an inner portion ofthe ink impregnated layer 52 is lower than a concentration in an outeredge of the ink impregnated layer 52. Accordingly, finally, thethree-dimensional shaped object 10 having high surface hardness and highinternal toughness is obtained. A part of the formation region 60 mayinclude a region to which the ink 5 is not supplied at all (a region inwhich the amount of carbon particles to be supplied is zero).

The average particle diameter of the carbon particles is preferably1/100000 or more and 1/100 or less, more preferably 1/50000 or more and1/500 or less, and still more preferably 1/10000 or more and 1/1000 orless of the average particle diameter of the Fe-based metal powder 1.Accordingly, it is easier for the carbon particles to penetrate intogaps between the particles of the Fe-based metal powder 1. Therefore,when the ink 5 is supplied to the formation region 60, the carbonparticles are easily distributed along the surfaces of the particles ofthe Fe-based metal powder 1. As a result, the quenching treatment to bedescribed later can be performed more uniformly.

2.4. Energy Ray Irradiating Step

In the energy ray irradiating step S206, as shown in FIG. 19 , theenergy ray irradiating unit 27 irradiates the formation region 60including at least the ink impregnated layer 52 with the energy ray E.In the ink impregnated layer 52 irradiated with the energy ray E, theparticles of the Fe-based metal powder 1 are sintered to obtain asintered layer 71 shown in FIG. 20 . In the sintered layer 71, theparticles of the Fe-based metal powder 1 are sintered to form a metalsintered body.

2.5. Repeating Step

In the repeating step S208, the powder layer forming step S202, the inkimpregnating step S204, and the energy ray irradiating step S206 arerepeated one or more times until a laminated body formed by laminating aplurality of the sintered layers 71 has a predetermined shape.Accordingly, the three-dimensional metal sintered body 7 shown in FIG.21 is obtained.

2.6. Quenching Step

In the quenching step S210, similar to the quenching step S112 of thefirst embodiment, a quenching treatment is performed on the metalsintered body 7. Accordingly, the three-dimensional shaped object 10shown in FIG. 16 is obtained. In the second embodiment, since energysupplied by the energy ray E is high, the quenching treatment may becompleted at the same time with the completion of the energy rayirradiating step S206. In this case, this step may be omitted, or thisstep may be performed and then a re-quenching treatment may beperformed. In addition, similar to the first embodiment, a temperingtreatment may be performed after the quenching treatment.

2.7. Effects of Second Embodiment

As described above, the method of manufacturing the three-dimensionalshaped object according to the second embodiment includes the powderlayer forming step S202, the ink impregnating step S204, the energy rayirradiating step S206, the repeating step S208, and the quenching stepS210. In the powder layer forming step S202, the Fe-based metal powder 1is leveled on the shaping stage 23 (on the table) to form the powderlayer 31. In the ink impregnating step S204, the formation region 60 ofthe powder layer 31 corresponding to the metal sintered body 7 to beformed is impregnated with the ink 5 containing carbon particles suchthat the amount of the carbon particles to be supplied is partiallyvaried, so as to obtain the ink impregnated layer 52. In the energy rayirradiating step S206, the formation region 60 including at least theink impregnated layer 52 is irradiated with the energy ray E to obtainthe sintered layer 71. In the repeating step S208, the powder layerforming step S202, the ink impregnating step S204, and the energy rayirradiating step S206 are repeated one or more times to obtain the metalsintered body 7 in which the plurality of sintered layers 71 arelaminated. In the quenching step S210, the quenching treatment isperformed on the metal sintered body 7 to obtain the three-dimensionalshaped object 10.

According to such a configuration, by partially varying the amount ofthe carbon particles supplied to the formation region 60, it is possibleto partially vary the degree of quenching in the finally obtainedthree-dimensional shaped object 10, that is, the hardness of thequenched structure. Accordingly, for example, in the vicinity of thesurface of the three-dimensional shaped object 10, the degree ofquenching can be increased to increase the hardness. On the other hand,inside the three-dimensional shaped object 10, the degree of quenchingcan be decreased to prevent an increase in the hardness. As a result, itis possible to implement the three-dimensional shaped object 10 havinghigh surface hardness and high internal toughness. In such athree-dimensional shaped object 10, both the high toughness and the highhardness are achieved, and thus, for example, both wear resistance anddurability are achieved.

In addition, according to the above-described method, it is possible toenjoy the advantage of the selective laser sintering method, which is alamination shaping method, without impairing the advantage of theselective laser sintering method. Therefore, for example, a regionhaving a cavity therein can be set as the formation region 60.Accordingly, a weight of the formation region 60 can be reduced, andfinally, the three-dimensional shaped object 10 having high surfacehardness and a light weight can be obtained.

In addition, in the method of manufacturing the three-dimensional shapedobject according to the second embodiment, the ink 5 is applied suchthat the amount of the carbon particles supplied to the outer edgeportion of the formation region 60 is larger than the amount of thecarbon particles supplied to a portion other than the outer edge portionof the formation region 60.

By shaping the metal sintered body 7 using the formation region 60obtained in this manner and finally obtaining the three-dimensionalshaped object 10, it is possible to efficiently manufacture thethree-dimensional shaped object 10 having high surface hardness and highinternal toughness.

In addition, by providing a gradient in which the concentration of thecarbon particles continuously changes, it is possible to preventoccurrence of cracking or the like due to a difference in thermalexpansion between a quenched structure layer in the vicinity of thesurface and the internal metal structure in the three-dimensional shapedobject 10. Accordingly, reliability of the three-dimensional shapedobject 10 can be improved.

3. Third Embodiment

Next, a three-dimensional shaped object according to a third embodimentwill be described.

FIG. 22 is a cross-sectional view schematically showing a distributionof a carbon concentration in the three-dimensional shaped object 10according to the third embodiment.

Hereinafter, the third embodiment will be described, and in thefollowing description, differences from the first embodiment will bemainly described, and description of similar matters will be omitted.

In the three-dimensional shaped object 10 shown in FIG. 22 , the carbonconcentration is represented by a density of dots. The three-dimensionalshaped object 10 is made of a sintered material of the Fe-based metalpowder 1. The three-dimensional shaped object 10 has a portion 19 inwhich the carbon concentration decreases from an outer surface 11 towardan inner portion 12. In the present embodiment, the entirety of thethree-dimensional shaped object 10 is formed by the portion 19. Only apart of the three-dimensional shaped object 10 may be formed by theportion 19, and the other portions may be formed by other structures.Examples of the other structure include a structure having a constantcarbon concentration.

As described above, the three-dimensional shaped object 10 according tothe present embodiment is made of the sintered material of the Fe-basedmetal powder 1, and has the portion 19 in which the carbon concentrationdecreases from the outer surface 11 toward the inner portion 12.

According to such a configuration, it is possible to achieve both highhardness of the outer surface 11 and high toughness of the inner portion12.

In addition, in the portion 19, as described above, it is preferablethat the strength of the gradient in which the carbon concentrationdecreases is partially varied.

According to such a configuration, for example, when the portion 19includes a locally thinned portion and a portion thicker than thelocally thinned portion, it is possible to achieve both the highhardness of the outer surface 11 and the high toughness of the innerportion 12. That is, if the gradient of the carbon concentration isgentle in the thinned portion, a range of the outer surface 11 is toothick, a volume of the inner portion 12 is relatively small, and it isdifficult to achieve both the high hardness and the high toughness.Therefore, in such a portion, it is easy to achieve both the highhardness and the high toughness by increasing the gradient of the carbonconcentration.

The carbon concentration in the outer surface 11 is preferably 0.2% bymass or more, and more preferably 0.3% by mass or more and 2.2% by massor less. When the carbon concentration is within the above range, ametal structure of the outer surface 11 can be satisfactorily quenched.Accordingly, it is possible to more reliably increase the hardness ofthe outer surface 11.

The carbon concentration in the outer surface 11 is measured by, forexample, an electron probe microanalyzer (EPMA) method.

FIG. 23 is a top view schematically showing a distribution of a carbonconcentration in a three-dimensional shaped object 10A according to amodification.

The three-dimensional shaped object 10A shown in FIG. 23 is a spur gearhaving a plurality of external teeth 13 and a shaft hole 14. Each of theexternal teeth 13 has a tooth surface 15. The external teeth 13 meshwith external teeth of other gears (not shown) to transmit rotation.Therefore, the tooth surface 15 rubs against teeth surfaces of othergears, thereby causing wear. Therefore, the three-dimensional shapedobject 10A is configured such that a carbon concentration decreases fromthe tooth surface 15 toward an inner portion thereof. In FIG. 23 , agradient of the carbon concentration in the tooth surface 15 isrepresented by an inclination of an arrow C3.

The carbon concentration also decreases from an inner surface 16 of theshaft hole 14 toward the inner portion. A gradient of the carbonconcentration in the inner surface 16 of the shaft hole 14 isrepresented by an inclination of an arrow C4. A shaft (not shown) isinserted into the shaft hole 14. Therefore, a friction between a surfaceof the shaft hole 14 and the shaft is small.

Therefore, the inclination of the arrow C3 is preferably steeper thanthe inclination of the arrow C4. Accordingly, the tooth surface 15 canhave hardness higher than that of the inner surface 16. On the otherhand, the inner surface 16 can have toughness higher than that of thetooth surface 15. Therefore, according to the three-dimensional shapedobject 10A of the modification, it is possible to obtain a gear that isexcellent in wear resistance of the tooth surface 15 and durability ofthe shaft hole 14 and that has a long life.

When the three-dimensional shaped object 10A is manufactured asdescribed above, the ink 5 may be applied such that the strength of thegradient in which the amount of the carbon particles decreases from theouter edge portion toward the inner portion of the formation region 60shown in FIG. 8 is partially varied. That is, the inclination of thearrow C3 representing the gradient of the carbon concentration in thetooth surface 15 may be different from the inclination of the arrow C4representing the gradient of the carbon concentration in the innersurface 16. As shown in FIG. 23 , the arrow C3 represents a gradient ofthe carbon concentration in a cross section that crosses the toothsurface 15 and couples a point D1 and a point D2. The arrow C4represents a gradient of the carbon concentration in a cross sectionthat crosses the inner surface 16 and couples a point D3 and a point D4.

According to such a configuration, when the manufacturedthree-dimensional shaped object 10A is applied to the gear, the hardnessof the tooth surface 15 can be increased, and the toughness of the innersurface 16 of the shaft hole 14 can be increased at the same time. As aresult, it is possible to easily obtain a gear having a long life.

The three-dimensional shaped objects 10 and 10A as described above canbe used as all or a part of, for example, transportation equipment partssuch as automobile parts, bicycle parts, railroad vehicle parts, shipparts, aircraft parts, and space transportation parts, electronic deviceparts such as personal computer parts, mobile phone terminal parts,tablet terminal parts, and wearable terminal parts, parts for electricalequipment such as refrigerators, washing machines, and air conditioners,machine parts such as machine tools and semiconductor manufacturingequipment, parts for plants such as nuclear power plants, thermal powerplants, hydropower plants, refineries, and chemical complexes, watchparts, metal tableware, and ornaments such as jewelry and eyeglassframes.

The method of manufacturing the three-dimensional shaped object and thethree-dimensional shaped object according to the present disclosure havebeen described above based on the illustrated embodiments, but thepresent disclosure is not limited thereto. For example, thethree-dimensional shaped object according to the present disclosure maybe an object in which any component is added to the above-describedembodiments.

In addition, the method of manufacturing the three-dimensional shapedobject according to the present disclosure may be a method in which anydesired step is added to the above-described embodiments.

What is claimed is:
 1. A method of manufacturing a three-dimensionalshaped object, the method comprising: a powder layer forming step ofleveling a Fe-based metal powder on a table to form a powder layer; abinder applying step of applying a binder solution containing a binderto a formation region of the powder layer corresponding to alaminate-shaped body to be formed; an ink applying step of applying anink containing carbon particles to the formation region such that anamount of the carbon particles supplied to the formation region ispartially varied; a repeating step of repeating the powder layer formingstep, the binder applying step, and the ink applying step one or moretimes, when the formation region to which the binder solution and theink are applied is set as a unit layer, to obtain the laminate-shapedbody in which a plurality of the unit layers are laminated; a sinteringstep of performing a sintering treatment on the laminate-shaped body toobtain a metal sintered body; and a quenching step of performing aquenching treatment on the metal sintered body to obtain athree-dimensional shaped object.
 2. The method of manufacturing athree-dimensional shaped object according to claim 1, wherein the ink isapplied such that an amount of the carbon particles supplied to an outeredge portion of the formation region is larger than an amount of thecarbon particles supplied to a portion other than the outer edge portionof the formation region.
 3. The method of manufacturing athree-dimensional shaped object according to claim 2, wherein the ink isapplied such that a strength of a gradient in which the amount of thecarbon particles decreases from the outer edge portion toward an innerportion of the formation region is partially varied.
 4. The method ofmanufacturing a three-dimensional shaped object according to claim 1,wherein in the repeating step, when the unit layers are laminated, theamount of the carbon particles is varied between the formation regions.5. The method of manufacturing a three-dimensional shaped objectaccording to claim 1, wherein the amount of the carbon particles to besupplied is adjusted by applying the ink such that a carbonconcentration in the three-dimensional shaped object is 0.2% by mass ormore.
 6. The method of manufacturing a three-dimensional shaped objectaccording to claim 1, wherein an average particle diameter of the carbonparticles is 1/100000 or more and 1/100 or less of an average particlediameter of the Fe-based metal powder.
 7. The method of manufacturing athree-dimensional shaped object according to claim 1, wherein the inkapplying step includes, when the ink is dispensed as a liquid dropletfrom a plurality of aligned nozzles, an operation of partially varyingthe amount of the carbon particles by changing a density of the liquiddroplet dispensed in a unit area.
 8. The method of manufacturing athree-dimensional shaped object according to claim 1, wherein the binderapplying step and the ink applying step are simultaneously performed byapplying a liquid containing both the binder and the carbon particles tothe formation region.
 9. The method of manufacturing a three-dimensionalshaped object according to claim 1, wherein the sintering step and thequenching step are continuously performed by continuously performing thesintering treatment and the quenching treatment without lowering atemperature of the laminate-shaped body to room temperature.
 10. Amethod of manufacturing a three-dimensional shaped object, the methodcomprising: a powder layer forming step of leveling a Fe-based metalpowder on a table to form a powder layer; an ink impregnating step ofimpregnating a formation region of the powder layer corresponding to ametal sintered body to be formed with an ink containing carbon particlessuch that an amount of the carbon particles to be supplied is partiallyvaried, so as to obtain an ink impregnated layer; an energy rayirradiating step of irradiating the formation region including at leastthe ink impregnated layer with an energy ray to obtain a sintered layer;a repeating step of repeating the powder layer forming step, the inkimpregnating step, and the energy ray irradiating step one or more timesto obtain the metal sintered body in which a plurality of the sinteredlayers are laminated; and a quenching step of performing a quenchingtreatment on the metal sintered body to obtain a three-dimensionalshaped object.
 11. The method of manufacturing a three-dimensionalshaped object according to claim 10, wherein the ink is applied suchthat an amount of the carbon particles supplied to an outer edge portionof the formation region is larger than an amount of the carbon particlessupplied to a portion other than the outer edge portion of the formationregion.
 12. The method of manufacturing a three-dimensional shapedobject according to claim 10, wherein an average particle diameter ofthe carbon particles is 1/100000 or more and 1/100 or less of an averageparticle diameter of the Fe-based metal powder.
 13. The method ofmanufacturing a three-dimensional shaped object according to claim 1,further comprising: an operation of compressing the powder layer in athickness direction.
 14. A three-dimensional shaped object made of asintered material of a Fe-based metal powder and having a portion inwhich a carbon concentration decreases from an outer surface toward aninner portion.
 15. The three-dimensional shaped object according toclaim 14, wherein a strength of a gradient in which the carbonconcentration decreases is partially varied.
 16. The three-dimensionalshaped object according to claim 14, wherein the carbon concentration inthe outer surface is 0.2% by mass or more.